In the gathering dusk, amid the floodlights and the candles, Pope Benedict XVI tonight told tens of thousands of Roman Catholics assembled in Hyde Park they too were suffering for their faith and compared them to the martyrs who were cruelly executed at nearby Tyburn. Their fate, he said, was not to be put to death but to be "dismissed out of hand, ridiculed or parodied".

His remarks sounded a sombre note in an otherwise joyful celebration of faith and fellowship with around 80,000 Catholics enjoying autumnal sunshine and a party atmosphere.

The pope said: "Not far from here, at Tyburn, great numbers of our brothers and sisters died for the faith. In our own time, the price to be paid for fidelity to the gospel is no longer being hanged, drawn and quartered, but it often involves being dismissed out of hand, ridiculed and parodied."

The pope warned, however, that "the church cannot withdraw from the task of proclaiming Christ and his gospel as saving truth, the source of our ultimate happiness as individuals and as the foundation of a just and humane society".

Benedict's comments echoed a central theme of his visit and, indeed, of his papacy – the marginalisation of Christianity in European public life.

The crowds were treated to a multi-cultural evening that reflected the racial diversity of London that Cardinal Walter Kasper claimed he was referring to when he said that landing at Heathrow was like arriving in a "Third World" country. There was a Swahili hymn and one, We Are Marching, that was translated from Afrikaans.

There were hymns, too, from West Cameroon in addition to more traditional fare, such as the Litany of the Sacred Heart and a hymn, Lead, Kindly Light, by Cardinal John Henry Newman. Today's event was a prayer vigil in preparation for tomorrow's mass at Cofton Park in Birmingham at which Newman, who converted to Catholicism from Anglicanism, will be beatified, moving one step closer to sainthood.

It will be the first beatification ever to be performed in this country and the first by Benedict, who has until now limited himself to taking part only in the canonisation of saints.

This backdrop of sanctity and symbolism did not get in the way of the organisers calling on the talents of television number cruncher Carol Vorderman and a finalist from a reality TV talent show, Liam McNally. The vigil gave Catholics a rare opportunity to dominate the Saturday evening television schedules. Performers were told to avoid wearing white clothes, stripes or prints because the cameras would react badly to them.

The pilgrims used social networking and rolling news channels to express their happiness at being at the event. Early estimates put the numbers in Hyde Park at around 80,000. The 83-year-old pope arrived in Hyde Park from a Catholic-run residence for the elderly, where he made a rare allusion to his own advanced age and the problems – and benefits – it brought him.

He said: "I come among you not only as a father, but also as a brother who knows well the joys and struggles that come with age. Our long years of life afford us the opportunity to appreciate both the beauty of God's greatest gift to us, the gift of life, as well as the fragility of the human spirit."

The pope added: "As the normal span of our lives increases, our physical capacities are often diminished; and yet these times may well be among the most spiritually fruitful years of our lives."

Benedict said it was important that the growing number of older people in society was seen as a blessing. "Every generation can learn from the experience and wisdom of the generation that preceded it. Indeed, the provision of care for the elderly should be considered not so much an act of generosity as the repayment of a debt of gratitude."

Between his main morning engagement – a mass in Westminster Cathedral – and his visit to the residence, there was a long gap in his itinerary that encouraged speculation he might be using it to meet some of the victims of sex abuse by priests that has dragged his church into its most serious crisis in modern times.

His spokesman, Father Federico Lombardi, said the pope was happy with the way the visit had gone so far, but added that Benedict had always been optimistic.

"We know that there are groups that have criticism for the pope and the Catholic church and that they have the right and the freedom to express it," he said.

"But we try always to have a general evaluation of the situation. And in this sense, I think that we recognize the reality is there is a very, very large audience that is very happy to meet the pope and express a great joy. I am very happy about the visit in general."